The overall objective of the proposed research is to determine the photobiological mechanisms by which short wavelength light and near ultraviolet (UV) radiation cause, or contribute to, retinopathy and senile cateract in primates (rhesus monkeys) after long term exposures to low levels of radiation. A 2500 watt xenon lamp, quartz optical system with associated filters and mirrors provides the radiation source. Retinal photopathology, the inflammatory response (pigmentary retinochoroiditis) and repair of retinal lesions will be studied using light optical and electron microscopy, anti-inflammatory and photosensitizing agents and dark adaptation. The role of melanin pigmentation will be determined (albino vs pigmented rabbits), and the mascular vs paramacular regions will be compared to study the effects on rods vs cones and the protective role of yellow macular pigment. Effects on the lens of daily repeated exposures to one eye, using the other eye as control, will be studied by measuring quantitatively, lens transmissivity and fluorescence, both of which have been shown to increase in the lens prior to the onset of senile cataract. Minimal repair mechanims in the slowly metabolizing lens make it vulnerable to cumulative photic insult. Once the lens has been removed, the retina is exposed to near UV radiation. Effects of near UV on the retina of aphakic monkeys will be studied by the methods outlined above for photoinduced retinopathy. If possible an action spectrum for UV effects on the retina will be determined using aphakic eyes.